The primary purpose of this proposal is to study prospectively smokeless tobacco users attempting cessation of use and determine factors predictive of relapse and abstinence. One hundred and fifty snuff users will be recruited. Prior to attempting to quit, subjects will be interviewed to assess history and extent of snuff use, use of other substances, cues or triggers of use, knowledge of health risks, history of previous quit attempts, and proposed self-determined strategies and self-efficacy to quit. Saliva cotinine levels and a measure of nicotine addiction also will be obtained prior to the subject's attempt at quitting. Subjects will then be followed for one year after their quit date and assessed at days 7, 30, 90, 180 and 365. Longitudinal assessment will include self-report of withdrawal symptoms, use of other substances, snuff use and relapse conditions in relapsers, and useful strategies used to remain abstinent in abstainers. Saliva samples will be obtained at each assessment but only one of the five samples will be selected for cotinine analysis; the other samples will serve as a bogus condition to enhance validity of the self-reports. Using logistic regressions and survival analyses, initial variables will be used as predictors of subsequent relapse or abstinence. We hypothesize that relapse will be predicted by greater recent use of snuff, higher addiction scores, lower perceived health risk, greater use of other substances, more social contacts who use snuff, greater cues for use (particularly internal cues), more previous failures at quitting, and lower self-efficacy at quitting. Higher initial cotinine levels also should be predictive of early relapse. The results of this study will aid our understanding of snuff addiction and relapse, which should result in more effective interventions for this major cause of oral and pharyngeal cancers.